1. Field of the Invention
The present invention relates to optical sources that can, for example, be used in optical wavelength division multiplexing (WDM) communication systems.
2. Description of the Related Art
Light sources are used in many fields, e.g., optical communications, metrology, medicine, and natural sciences. Many applications related to these fields make use of multiple light sources that have correlated properties, e.g., predetermined wavelength and/or phase relationships. However, the systems and methods for creating suitable correlated light sources are not sufficiently developed yet.
For example, in optical communications, a phase-shift keying (PSK)-modulated signal can be decoded at the receiver using homodyne detection, in which a local oscillator (LO) signal having a well-defined phase relationship with the received signal is utilized. However, one problem with the use of homodyne PSK in a WDM communication system is that homodyne detection utilizes a separate phase-locked LO signal for each WDM wavelength. In a typical prior-art WDM system, the task of providing these separate phase-locked LO signals for the WDM wavelengths carries the burden of providing separate light sources and phase-lock loops for different wavelengths, which can add significantly to the complexity, size, and cost of each transceiver. This burden might substantially prohibit the use of homodyne PSK in WDM systems having a relatively large number (e.g., greater than about 20) of WDM channels.